The field of this invention relates to the welding of separate metallic tubular members by a known welding technique such as a gas shielded, tungsten, electro-arc welding process. More particularly, this invention relates to a welding apparatus which is preprogramed to automatically weld a particular exteriorly configured structure to produce an extremely strong weld not having any flaws throughout the entire length of the weld.
The use of equipment to automatically weld cylindrical members has been known previously. An example of such an automatic welding device is shown and disclosed within U.S. Pat. No. 3,777,115, issued Dec. 4, 1973, entitled APPARATUS FOR CONTROLLING ELECTRODE OSCILLATION. In such a welding apparatus, the location of the welding electrode, must be precisely controlled. This precise control, in order to achieve optimum quality weld, is concerned with the distance the welding electrode is from the weld area, the arc voltage, the welding current and so forth.
In the welding of a cylinder, the welding head only need move in a circular path about the exterior cylindrical surface of the workpiece. Because the exterior surface of the workpiece is cylindrical, the welding procedure is somewhat simplified.
However, what if the cylindrical surface of the workpiece is not cylindrical, that is, polygonal shaped, or elliptically shaped, or any shape other than cylindrical. Previous to this invention there was not known an automatic welding device capable of welding such shapes. The reason for this was that there are sharp corners in a polygonal shaped workpiece which would require the welding electrode to move around the corners and it would be very difficult to maintain the precise spacing of the welding electrode from the weld area in order to achieve the optimum weld quality.
Since a great many tubular structures are not cylindrical, it would be desirable to design some form of welding apparatus which could automatically weld non-cylindrical tubular members and produce a flawless weld.